System and Method for Injector Fault Remediation

ABSTRACT

A machine includes an engine having an exhaust system. A diesel exhaust fluid (DEF) injector provides metered amounts of DEF and includes a valve adapted to selectively open in response to a command. A controller associated with the engine and the DEF injector monitors operation of the DEF injector to detect a fault and activates a failure remediation cycle when the fault has been detected. The remediation cycle includes heating the exhaust gas to heat the DEF injector and melt any urea crystals that may be causing the fault, and activating the valve of the DEF injector to evacuate molten urea from within the DEF injector.

TECHNICAL FIELD

This disclosure relates generally to engine systems and, more particularly, to exhaust after-treatment systems and methods.

BACKGROUND

One known method for abating certain diesel engine exhaust constituents is by use of an exhaust after-treatment system that utilizes Selective Catalytic Reduction (SCR) of nitrogen oxides. In a typical SCR system, urea or a urea-based water solution is mixed with exhaust gas. In some applications, a urea solution is injected directly into an exhaust passage through a specialized injector device. The injected urea solution mixes with exhaust gas and breaks down to provide ammonia (NH₃) in the exhaust stream. The ammonia then reacts with nitrogen oxides (NO_(x)) in the exhaust at a catalyst to provide nitrogen gas (N₂) and water (H₂O).

As can be appreciated, SCR systems require the presence of some form of urea close to the engine system such that the engine can be continuously supplied during operation. Various urea or urea-solution delivery systems are known and used in engine applications. In known urea injection systems, temperature- and/or pressure-related challenges may arise that can affect the electronic and mechanical hardware used to inject the urea. For example, given that the urea is typically injected directly into the engine's exhaust system in an aqueous solution form, changes in the solution concentration due to thermal or pressure effects can impede proper injector function both during system operation as well as after heat saturation following a hot engine shut-down. Moreover, for systems using water-based urea solutions, boiling and/or depressurization of the system can result in crystallization of urea at the injector, which may plug the injector.

SUMMARY

The disclosure describes, in one aspect, a machine. The machine includes an engine having an exhaust system associated therewith. A diesel exhaust fluid (DEF) injector is disposed to provide metered amounts of DEF into the exhaust system. The DEF injector includes a valve adapted to selectively open in response to a command for injecting DEF into the exhaust system. A controller is associated with the engine and the DEF injector. The controller is disposed to monitor operation of the DEF injector to detect a fault, activate a failure signal when a fault in the DEF injector is detected, and activate a failure remediation cycle while the failure signal is active. The remediation cycle includes causing an increase in a temperature of an exhaust gas in the exhaust gas system to heat the DEF injector and melt any urea crystals that may be causing the fault, and activating the valve of the DEF injector to evacuate molten urea from within the DEF injector. The controller furher determines whether the fault has been cleared, and resets the failure signal when the fault has been cleared.

In another aspect, the disclosure describes a method for failure remediation of a diesel exhaust fluid (DEF) injector in a machine having an engine, which includes an exhaust system. The method comprises generating exhaust gas and routing the same through an exhaust gas system. Predetermined quantities of a diesel exhaust fluid (DEF) containing an aqueous solution of urea are selectively injected into the exhaust gas using a DEF injector. The DEF injector is responsive to command signals provided by a controller. Operation of the DEF injector is monitored with the controller to detect a fault, and a failure signal is activated in the controller when a fault in the DEF injector is detected. A failure remediation cycle is activated in the controller while the failure signal is active. The remediation cycle includes causing an increase in a temperature of the exhaust gas in the exhaust gas system to heat the DEF injector above a normal operating temperature such that any urea crystals that may be causing the fault are melted. The DEF injector is then activated to evacuate molten urea from within the DEF injector.

In yet another aspect, the disclosure describes a method for remediating a fault in a DEF injector. The method includes determining that a fault is present in the DEF injector, which fault may be attributable to condensation of crystalline urea within the injector after boiling and evaporation of water from an aqueous urea solution has occurred within the DEF injector. A failure signal is activated when the fault in the DEF injector is present. The DEF injector is heated to a temperature that is above a normal operating temperature to melt any crystalline urea within the DEF injector. The DEF injector is activated to evacuate any molten urea from within the DEF injector, and a determination is made as to whether the fault has been remediated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outline view of a machine in accordance with the disclosure.

FIG. 2 is a block diagram of an engine having a SCR system in accordance with the disclosure.

FIG. 3 is a partially sectioned outline view of an exhaust treatment module in accordance with the disclosure.

FIG. 4 is an outline view of an injector for diesel exhaust fluid (DEF) in accordance with the disclosure.

FIG. 5 is a block diagram of a crystallization prevention and remediation control system in accordance with the disclosure.

FIG. 6 is a block diagram of an alternative embodiment of a control system in accordance with the disclosure.

FIG. 7 is a flowchart for a method of crystallization prevention and remediation in accordance with the disclosure.

DETAILED DESCRIPTION

This disclosure relates to power management systems for machines and, more particularly, to power management systems and methods that prevent and, if necessary, remediate DEF injector plugging due to urea crystallization.

A side view of a machine 100, in this example a motor grader 101, is shown in FIG. 1. The term “machine” is used generically to describe any machine having at least one drive wheel that is directly driven by a motor connected to the wheel, for example, by use of electrical or hydrostatic power, or is alternatively driven by mechanical means by an engine through a transmission. Although a motor grader is illustrated in FIG. 1, any machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, marine or any other industry known in the art is contemplated. For example, the machine 100 may be an earth-moving machine, such as a wheel loader, excavator, dump truck, backhoe, material handler, locomotive, paver or the like. Apart from mobile machines, the machine 100 may be a stationary or portable machine such as a generator set, an engine driving a gas compressor or pump, and the like. Similarly, although an exemplary blade is illustrated as the attached implement, an alternate implement may be included. Any implements may be utilized and employed for a variety of tasks, including, for example, loading, compacting, lifting, brushing, and include, for example, buckets, compactors, forked lifting devices, brushes, grapples, cutters, shears, blades, breakers/hammers, augers, and others.

The motor grader 101 shown in FIG. 1 generally includes a two-piece frame made up of an engine frame 102 and an implement portion 104. Alternatively, the motor grader 101 may include a single frame piece. The engine frame 102 in the embodiment shown is connected to the implement portion 104 by a pivot (not shown). The implement portion 104 includes an operator cab 106 and two idle wheels 108 (only one visible) that contact the ground. The engine frame 102 contacts the ground through two drive wheels 118, which are connected to one another by a tandem beam 120 that is connected to the engine frame 102 at a pivot 123. A shovel or blade 110 is suspended along a mid-portion of the implement portion 104. The blade 110 can be selectively adjusted to engage the ground at various heights and angles to achieve a desired grade or contour while the motor grader 101 operates. Adjustment of the position of the blade 110 is accomplished by a system of actuators, generally denoted in FIG. 1 as 112, while support for the loading experienced by the blade 110 during operation is accomplished by a bar 114, which pivotally connects the implement portion 104 to the blade 110.

The engine frame 102 supports an engine (shown and described relative to FIG. 2, below), which is protected from the elements by an engine cover 116. The engine provides the power necessary to propel the motor grader 101 as well as to operate the various actuators and systems of the motor grader 101. As can be appreciated, other machines may have different configurations and/or various other implements associated therewith. The engine cover 116 includes grates and other openings that allow air to pass over and cool engine components.

FIG. 2 is a block diagram of an exhaust after-treatment system 200 associated with the engine 202 of the machine 100. The system 200 may be modularly packaged as shown in the illustrated embodiment for retrofit onto existing engines or, alternatively, for installation on new engines. In the illustrated embodiment, the system 200 includes a first module 204 that is fluidly connected to an exhaust conduit 206 of the engine 202. During engine operation, the first module 204 is arranged to internally receive engine exhaust gas from the conduit 206. The first module 204 may contain various exhaust gas treatment devices such as a diesel oxidation catalyst (DOC) 208 and a diesel particulate filter (DPF) 210, but other devices may be used. The first module 204 and the components found therein are optional and may be omitted for various engine applications in which the exhaust-treatment function provided by the first module 204 is not required. In the illustrated embodiment, exhaust gas provided to the first module 204 by the engine 202 may first pass through the DOC 208 and then through the DPF 210 before entering a transfer conduit 212.

The transfer conduit 212 fluidly interconnects the first module 204 with a second module 214 such that exhaust gas from the engine 202 may pass through the first and second modules 204 and 214 in series before being released at a stack 220 that is connected to the second module. In the illustrated embodiment, the second module 214 encloses a SCR catalyst 216 and an Ammonia Oxidation Catalyst (AMOX) 218. The SCR catalyst 216 and AMOX 218 operate to treat exhaust gas from the engine 202 in the presence of ammonia, which is provided after degradation of a urea-containing solution injected into the exhaust gas in the transfer conduit 212.

More specifically, a urea-containing water solution, which is commonly referred to as diesel exhaust fluid (DEF) 221, is injected into the transfer conduit 212 by a DEF injector 222. The DEF 221 is contained within a reservoir 228 and is provided to the DEF injector 222 by a pump 226. As the DEF 221 is injected into the transfer conduit 212, it mixes with exhaust gas passing therethrough and is carried to the second module 214. To promote mixing of DEF with exhaust, a mixer 224 may be disposed along the transfer conduit 212.

As can be appreciated, the location of the DEF injector 222 on the transfer conduit 212 can expose the injector to relatively high temperatures due to heating from exhaust gas during operation. In the illustrated exemplary embodiment, a flow of engine coolant is provided through the injector, but such coolant flow is optional.

One issue that may arise during operation is crystallization of urea in the DEF, especially at the injector 222. Crystallization may occur, for example, when the DEF fluid is depressurized during system purge following engine shutdown. Specifically, when the DEF system is purged, pressure in the DEF conduits is reduced from an operating pressure value to a pressure close to atmospheric pressure. Given the relatively elevated temperature of the DEF injector 222 in this condition, and the pressure decrease, the boiling point of the solution is lowered, which in turn may cause water from the DEF solution to boil and evaporate. In certain conditions, the evaporated water may cause a super-saturated solution and/or solid urea crystals to form within the DEF injector. Such solids may have a particular melting temperature that can be predetermined and dependent on the chemical compounds or mixtures thereof that are prone to crystallization. Such crystallization may obstruct normal injector operation, for example, by physically blocking the opening of the injector valve and/or blocking DEF conduits within the injector that supply DEF to the valve for injection.

FIG. 3 is a partially sectioned outline view of the system 200, and FIG. 4 is an outline view of the DEF injector 222 removed from the system 200 for illustration. In reference to these figures, the present disclosure is aimed at addressing thermal issues associated with the DEF injector 222 and surrounding systems. For high temperature conditions, the disclosure provides, at least in part, a system and method for managing heat input to the injector, especially after purging operations that may create conditions suitable for the formation of solid urea condensates within the injector.

More specifically, the system 200 is packaged such that the position of the DEF injector 222 is relatively external to the surrounding structures and exposed to a convective cooling air flow both during operation of the engine as well as post-shutdown. In reference to FIG. 3, where same or similar structures as corresponding structures previously described are denoted by the same reference numerals previously used for simplicity, the first and second modules 204 and 214 are disposed next to one another, with the transfer conduit 212 disposed between them. The DEF injector 222 is disposed on an upstream end of the transfer conduit 212 relative to a direction of exhaust gas flow 302.

A controller 300 and various sensors are disposed to monitor and control operation of the system 200. More specifically, the system may include one or more temperature sensors disposed to measure exhaust temperature within the system 200 and provide temperature signals indicative of the temperatures measured to the controller 300. The controller 300 may be a single controller, as illustrated in FIG. 2, or may include more than one controller disposed to control various functions and/or features of a machine. For example, a master controller, used to control the overall operation and function of the machine, may be cooperatively implemented with a motor or engine controller, used to control the engine 202, a SCR system controller (not shown), used to control operation of the DEF injector 222 and pump 226, and other controllers.

In this embodiment, the term “controller” is meant to include one, two, or more controllers that may be associated with the machine 100 and that may cooperate in controlling various functions and operations of the machine 100 (FIG. 1). The functionality of the controller 300, while shown conceptually in the various figures to include various discrete functions for illustrative purposes only, may be implemented in hardware and/or software without regard to the discrete functionality shown. Accordingly, various interfaces of the controller are described relative to components shown in the block diagram of FIG. 2. Such interfaces are not intended to limit the type and number of components that are connected, nor the number of controllers that are described.

The controller 300 is associated with the DEF injector via a DEF injector command line 301, through which the controller may monitor and control the injector 222. The controller 300 may further be associated with one or more temperature sensors disposed to measure exhaust temperature within the system 200. In the illustrated embodiment, a first temperature sensor 304 is connected to the controller 300 via a first temperature communication line 306. The first temperature sensor 304 provides a first temperature signal to the controller 300 that is indicative of a temperature of exhaust gas entering the after-treatment system 200 during operation. As shown, the first temperature sensor 304 is disposed downstream of a regeneration assistance device 308, for example, a “Cat Regeneration System” (CRS), which is available from Caterpillar, Inc. of Peoria, Ill., and/or a back pressure device. Back pressure devices are typically embodied as a valve such as a butterfly valve or a moveable variable nozzle turbine arrangement, which can be arranged to selectively block the exhaust conduit of an engine thus increasing exhaust back pressure on the engine and also increasing exhaust temperature. At present, the CRS in the illustrated embodiment is an active regeneration system used in engines rated 130-560 bkW (175-750 bhp) to selectively elevate exhaust gas temperatures to promote oxidation and burn off soot in the DPF 210, as required. The CRS includes a fuel-fired heater that generates a flame within the exhaust system of the machine to thus increase the temperature of exhaust gas that passes therethrough. Activation and control of the CRS 308 can be provided by the controller 300 through a CRS control line 310. In the illustrated embodiment, the controller 300 is further associated with a second temperature sensor 312, which is connected to the controller 300 via a second temperature communication line 314 through which the second temperature sensor 312 provides a second temperature signal to the controller 300 that is indicative of a temperature of exhaust gas entering the SCR portion of the system 200.

It should be appreciated that any known mode of heating the exhaust gas of the engine may be used in addition to or instead of the heating devices described above. For example, post injection of fuel to provide hydrocarbons in the exhaust, whether those hydrocarbons are injected directly into the exhaust conduit of the engine or provided in the engine cylinders in a late-post injection, may interact with various after-treatment components, such as a DPF, oxidize, and thus increase exhaust temperature selectively during engine operation.

An outline view of one embodiment for the DEF injector 222 is shown in FIG. 4. In this embodiment, the injector 222 includes a body portion 230 that houses an electrical actuator (not shown), which can receive command signals through an electrical connector 232 connected to the body portion 230. The electrical connector 232 may be connected to the communication line 301 (FIG. 2). The actuator is connected to and operates a valve member 234. The valve member 234, when open, permits a flow of DEF out of the injector 222 and into the transfer conduit 212. A position sensor 235 provides a position signal indicative of the position of the valve 234 to the controller 300. In an alternative embodiment, a current signal provided to the electrical actuator is monitored to deduce the position of a spool within a solenoid actuator and thus deduce the position of the injector valve. In the event crystallized urea is present within the injector 222, the crystallized urea solids may fluidly and/or mechanically block the operating and/or the flow of DEF of the valve member 234. In the case of mechanical blocking, an actuator force provided by the actuator may be insufficient to break through deposits to open the valve member 234 when injection of DEF is desired. Similarly, in the case of fluid blocking, then opening the valve member 234 may not lead to a desired injection amount and timing of DEF if a sufficient flow of DEF cannot reach the valve member 234.

During normal operation, the injector 222 is generally protected from heat input to protect electronic and other components present therein from increased temperatures. To create a conductive heat transfer barrier between the body portion 230 and the exhaust system to which the injector 222 is connected to, a plurality of spacers 236 are used to space apart the body portion 230 from a mounting flange 238, thus creating a gap 240 between the body portion 230 of the injector 222 and the mounting flange 238.

DEF is supplied to the valve member 234 through the body portion 230. A DEF inlet conduit 242 is connected to a conduit 245 (FIG. 2), which is in turn fluidly connected to the reservoir 228. Under certain operating conditions, the flow of DEF through the injector 222 between the inlet conduit 242 and the valve member 234 acts to convectively cool the body portion 230 during operation. Additional convective cooling can further be provided by routing engine coolant or another cooling fluid through internal passages formed in the body portion 230. In the illustrated embodiment, an internal passage (not shown) extending through the body portion 230 is fluidly accessible through inlet and outlet coolant ports 244 and 246. Each coolant port 244 and 246 is connected to a respective conduit 248 and 250 (FIG. 5), which is adapted to receive a flow of coolant therethrough for convectively controlling a temperature of the body portion 230. In one aspect, the flow of coolant passing through the injector body may act to heat the injector so that any urea solids found therein can melt. However, such heating may not be sufficient to remediate a crystallization condition under all operating conditions.

In reference now to FIGS. 5 and 6, two block diagrams illustrating alternative embodiments crystallization prevention and remediation controllers are shown. In a first embodiment, as shown in FIG. 5, a controller 400 receives various inputs and, based on those inputs and other information, diagnoses failures and controls operation of the DEF injection and related systems of a machine. Inputs to the controller 400 in the illustrated embodiment include exhaust temperature 402, regeneration status 404, DEF injector valve position 406, engine speed (RPM) 408, engine load 410 and a diagnostic flag or past failure count 412, although fewer, more and/or different parameters may be used. On the basis of at least these or similar parameters, the controller 400 provides a command signal 414. The command signal 414 can include particular commands that control the operation of one or more components and systems of a machine. In the illustrated embodiment, the command signal 414 may include a DEF injector command, which is provided to the DEF injector, for example, the injector 222 via the communication line 301. The command signal 414 may further include information relative to activation, operation and/or control of the CRS 308 when exhaust temperature increase for regeneration of the DPF 210, crystallization prevention or remediation of the DEF injector 222 is desired, as described below.

As mentioned above, when the DEF system purges DEF from the DEF injector, for example, the injector 222, while the injector is hot, the injector becomes susceptible to boiling of the water in the DEF solution within the injector. The boiling may increase the urea concentration of the DEF fluid, which can cause the precipitation and crystallization of urea deposits within the injector, thus possibly causing a partial or full blockage of the injector and preventing proper operation. Such effects are generally referred to herein as a “fault” or a “failure” condition relative to the DEF injector or to the DEF dispensing system in general. The melting point of urea solids under typical precipitation conditions can be as high as 130 deg. C. The controller 400 is advantageously configured to detect such conditions when they occur, and to remediate any decreases in operational capability of the DEF injector such that the cost and time otherwise required for repair or replacement of the injector and other system components can be avoided.

In one embodiment, the controller 400 may attempt to reestablish operation of the injector 222. In this operating mode, the controller may establish that a potential failure condition in the injector is imminent or expected before the failure is manifested or detected. To accomplish this, the controller 400 may monitor the exhaust temperature signal 402 during a DEF purge event to determine whether conditions favorable for urea crystal precipitation are present. The controller may further anticipate an exhaust temperature increase if a forced regeneration operation is forthcoming as indicated, for example, by the regeneration signal 404. The DEF purge event may be identified via the diagnostic signal 412, or via a combination of a particular set of engine speed RPM 408 and engine load 410 with an opening of the injector valve, as indicated by the injector valve position 406. When a DEF purge is underway or forthcoming in the presence of high exhaust temperatures, the controller may establish that a urea crystallization remediation should be carried out at the next available opportunity.

Alternatively, a urea crystallization condition within the injector may be diagnosed by a fault indication provided by a controller or control algorithm that monitors and operates the DEF injector. Specifically, the controller 400 may monitor operation of the DEF injector on an ongoing basis during operation. At times when urea crystals are impeding operation of the injector, a diagnosis of a fault at the injector may be carried out by comparing, within the controller 400, the position of the injector valve 406 with an expected or predetermined position of that valve based on a valve command. In other words, the controller 400 may command a valve opening for the injector valve to inject DEF fluid, and then monitor the injector valve position 406 to ensure that the valve has indeed opened to the degree requested. In the event that the valve does not fully respond to the commands, a fault condition may be indicated, a malfunction indication 416 may be provided, and a remediation process may be initiated to correct the fault condition, if possible. In one embodiment, the controller may compare a commanded DEF injector valve position with an actual DEF injector valve position that is determined based on a position signal provided by a position sensor associated with the DEF injector valve. Based on this information, the controller may determine that the fault is present when a difference between the commanded and actual DEF injector valve positions exceeds a predetermined threshold for a predetermined period.

When carrying out a remediation operation, the controller 400 may first ensure that the system is operating, i.e., pressurized DEF is present in the injector and DEF injections are performed on an intermittent basis in accordance with a DEF injector control strategy. The operating mode may be a normal operating mode, if the controller has previously determined that conditions promoting urea crystallization may have been present in the past, or may alternatively be an operating mode under a fault condition, if the controller has already determined a fault condition to be present that impedes normal DEF injector operation. Prior to a commanded DEF injection based on, for example, engine speed 408 and load 410 signals, the controller may first cause a heating of the injector 222 to a temperature between 100 and 140 deg. C, for example, a temperature around 130 deg. C, at least temporarily. Such temperature increase may be sufficient to melt any urea crystals that may be present therein. Upon melting, an injection may be carried out to evacuate the high-concentration urea solution from the injector, and then the injector may be returned to a normal, lower operating temperature.

Heating of the exhaust gas for this purpose may be accomplished by various methods, for example, by activation of a CRS, by causing an increased load on the engine, by using an exhaust back-pressure valve disposed in the exhaust system to restrict engine exhaust, thus increasing engine load and exhaust temperature, and/or by other methods or a combination of methods. Alternatively, the controller may passively monitor exhaust temperature during normal service for excursions above a threshold temperature, for example 130 deg. C. In such a passive or opportunistic remediation operation, the controller may active the injector if and when such higher exhaust temperature conditions are present to evacuate the now-melted urea from the injector.

An alternative embodiment of a controller 500 is shown in FIG. 6. In this embodiment, the controller 500 cooperates with a DEF controller 502 in carrying out various system operations. In this arrangement, the controller 500 incorporates functionality that can be added onto existing systems that already have dedicated DEF injection system-controllers. Here, the role of the controller 500 augments operation of the DEF controller 502 by providing detecting and, more importantly, remediating DEF injector fault condition functionality, especially concerning crystallization plugging of the DEF injector. In the description that follows, elements that are the same or similar to corresponding elements previously described are denoted by the same reference numerals previously used for simplicity.

More specifically, the DEF controller 502 is configured to receive various signals including, for example, engine speed 408, engine load 410, and injector valve position 406. On the basis of information provided by these signals, and other information such as tabulated data, the DEF controller provides an injector command signal 411. The DEF controller 502 also monitors DEF injection system operation and, in the event of a fault, provides a fault signal 416.

The command signal 411 is intercepted by the controller 500. During normal operation, i.e., in the absence of detected faults, the controller 500 may receive the injector command signal 411 and pass it through to the injector unaltered as an injector command 414. When a fault is detected, for example, when the fault signal 416, which is also provided to the controller 500, is activated, the controller 500 may attempt to remediate the fault as previously described. In such conditions, the controller 500 may take over operation of the DEF injector, for example, the injector 222 (FIG. 2), as well as intervene in the operation of other machine systems in an attempt to cure the fault condition.

During operation under a failure remediation mode, the controller 500 may independently provide activation signals to the DEF injector, via the command signal 414, as well as cause other machine and/or engine systems to operate in a remediation mode, on the basis of information provided to the controller 500 by various input signals including exhaust temperature 402 and a time or event counter 412. As in the previously described embodiment relative to FIG. 5, the command signal 414 may further include information relative to activation, operation and/or control of the CRS 308 when exhaust temperature increase for regeneration of the DPF 210, crystallization prevention or remediation of the DEF injector 222 is desired.

When a fault condition is present, the controller 500 may first attempt to reestablish operation of the injector when the controller 500 determines that urea crystallization remediation should be carried out. When carrying out a remediation operation, the controller 500 may first ensure that the system is operating, i.e., pressurized DEF is present in the injector and DEF injections are performed on an intermittent basis in accordance with a DEF injector control strategy. The controller may cause a heating of the injector 222 to a temperature between 100 and 140 deg. C, for example, a temperature around 130 deg. C, at least temporarily. Such temperature increase may be sufficient to melt any urea crystals that may be present therein. Upon melting, an injection may be carried out to evacuate the high-concentration urea solution from the injector, and then the injector may be returned to a normal, lower operating temperature.

Heating of the exhaust gas for this purpose may be accomplished by various methods, for example, by activation of the CRS, by causing an increased load on the engine, by using the exhaust back-pressure valve disposed in the exhaust system to restrict engine exhaust, and/or by other methods or a combination of methods. Alternatively, the controller may passively monitor exhaust temperature during normal service for excursions above a threshold temperature, for example 130 deg. C. In such a passive or opportunistic remediation operation, the controller may active the injector if and when such higher exhaust temperature conditions are present to evacuate the now-melted urea from the injector.

The controller 500 may attempt to remediate a failure condition within a predetermined period following activation of the failure signal 416, for example, a period of about 1 hour. During this time, the failure signal 416 may retain active a warning system for the machine operator that the machine DEF injection system requires service. Within this time, the controller 500 may attempt to cause the machine to undergo a remediation cycle, which includes heating the injector, for example, by increasing exhaust temperature, and activating the heated injector to dispose of now-melted urea crystals that may be present therein. The controller 500 may attempt to complete one such full cycle during the 1-hour remediation period. If the remediation cycle is successful, the DEF controller 502 may regain normal system operation and deactivate the fault signal 416. If the remediation cycle is unsuccessful, the controller 500 may complete its remediation attempt without success and the fault signal 416 can remain active until the system is serviced. It is noted here that the DEF controller 502 may include active remediation functionality such as attempting to test system operation intermittently during a failure period.

Industrial Applicability

The present disclosure is applicable to emission control systems for engines and, more particularly, to emission control systems using SCR processes requiring the injection of urea-based water solutions into engine exhaust streams. A flowchart for a method of remediating a fault in the urea injection components of such systems is shown in FIG. 7 and described below.

In reference to FIG. 7, the remediation process begins with the diagnosis of a fault in a DEF injector at 602. Although many different failure types may be diagnosed, relevant to the present disclosure are conditions involving plugging and/or sticking of the DEF injector, which may be attributable to urea crystallization within the DEF injector. When such a condition is diagnosed, a remediation time counter may be initiated at 604, a failure signal may be provided at 606, for example, to a machine operator notifying the same of the failure condition, and a remediation mode of operation may be initiated at 608.

The remediation cycle includes checking whether a maximum remediation period has elapsed at 610 and, if it has, a failure flag is set at 624 and the process is terminated. While the remediation period is running, the exhaust temperature of the engine is progressively increased at 614. The temperature of the DEF injector is monitored and/or estimated at 616. While the injector is being heated, the injector is activated or cycled to evacuate any molted urea found therein at 618. Following injector activation, a functional test of the injector is carried out at 620 and, if the injector is functional, the exhaust temperature and thus the injector temperature is lowered at 622 towards a normal operating temperature and the process ends. If the failure remains, the exhaust heating and injector cycling procedures persist until the remediation period has elapsed at 610, at which time the failure flag is set at 624 and the process ends.

It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 

We claim:
 1. A machine, comprising: an engine having an exhaust system associated therewith; a diesel exhaust fluid (DEF) injector disposed to provide metered amounts of DEF into the exhaust system, the DEF injector including a valve adapted to selectively open in response to a command for injecting DEF into the exhaust system; and a controller associated with the engine and the DEF injector; wherein the controller is disposed to: monitor operation of the DEF injector to detect a fault; activate a failure remediation cycle when a fault is detected, said remediation cycle including causing an increase in a temperature of an exhaust gas in the exhaust gas system to heat the DEF injector and melt any urea crystals that may be causing the fault, and activating the valve of the DEF injector to evacuate molten urea from within the DEF injector; determine whether the fault has been cleared; and when the fault is present for a predetermined period, set a failure flag signal.
 2. The machine of claim 1, further comprising a temperature sensor disposed to measure the temperature of the exhaust gas in the exhaust gas system and provide a temperature signal to the controller, wherein the controller is further disposed to estimate a temperature of the DEF injector based on the temperature signal.
 3. The machine of claim 1, wherein causing the increase in the temperature of the exhaust gas is accomplished by at least one of activating an exhaust gas heater device, increasing a back pressure of the engine, and providing unburned hydrocarbons in the exhaust gas system.
 4. The machine of claim 1, wherein the controller is further disposed to: determine an actual DEF injector valve position; compare a commanded DEF injector valve position with the actual DEF injector valve position, and determine that the fault is present when a difference between the commanded and actual DEF injector valve positions exceeds a predetermined threshold difference for a predetermined period.
 5. The machine of claim 1, further comprising a device disposed along the exhaust system and operable to increase the temperature of the exhaust gas in response to a command signal from the controller.
 6. The machine of claim 5, wherein the device includes a fuel fired heater configured to produce a flame within the exhaust system to thus increase the temperature of the exhaust gas.
 7. The machine of claim 5, wherein the device is a back-pressure device, which includes a valve disposed to selectively block the exhaust system against flow of exhaust gas therein, which operates to increase engine exhaust back-pressure and thus increase engine load and the temperature of the exhaust gas.
 8. The machine of claim 1, wherein the controller is configured to cause the increase in temperature of the exhaust gas by providing commands arranged to increase at least one of a speed and load outputs of the engine.
 9. A method for failure remediation of a diesel exhaust fluid (DEF) injector in a machine having an engine, the engine having an exhaust system, the method comprising: generating exhaust gas and routing the same through an exhaust gas system; selectively injecting predetermined quantities of a diesel exhaust fluid (DEF) containing an aqueous solution of urea into the exhaust gas using a DEF injector that is responsive to command signals provided by a controller; monitor operation of the DEF injector with the controller to detect a fault; activate a failure signal in the controller when a fault in the DEF injector has been present for a predetermined period; activate a failure remediation cycle in the controller while the failure signal is active and before the predetermined period has expired, said remediation cycle including causing an increase in a temperature of the exhaust gas in the exhaust gas system; heating the DEF injector above a normal operating temperature but below a high temperature threshold; melting any urea crystals that may be causing the fault; and activating the DEF injector to evacuate molten urea from within the DEF injector.
 10. The method of claim 9, further comprising: determining whether the fault has been cleared; and resetting the failure signal when the fault has been cleared.
 11. The method of claim 9, further comprising measuring the temperature of the exhaust gas, and providing a temperature signal to the controller, wherein heating the DEF injector above a normal operating temperature includes estimating a temperature of the DEF injector in the controller based on the temperature signal.
 12. The method of claim 9, further comprising determining an opening state of a valve of the DEF injector, and providing a position signal to the controller, wherein detecting a fault is accomplished at least in part on the basis of the position signal.
 13. The method of claim 12, wherein detecting the fault is accomplished by: comparing a commanded DEF injector valve position with an actual DEF injector valve position, which is established based on the position signal, and determining that the fault is present when a difference between the commanded and actual DEF injector valve positions exceeds a predetermined threshold difference for a predetermined period.
 14. The method of claim 9, wherein heating the DEF injector above a normal operating temperature is accomplished by causing the temperature of the exhaust gas to increase by activating a device disposed along the exhaust system and operable to increase the temperature of the exhaust gas in response to a command signal from the controller.
 15. The method of claim 14, wherein the device includes a fuel fired heater configured to produce a flame within the exhaust system to thus increase the temperature of the exhaust gas.
 16. The method of claim 14, wherein the device is a back-pressure device, which includes a structural arrangement disposed to selectively block the exhaust system against flow of exhaust gas therethrough, and which operates to increase engine exhaust back-pressure and thus increase engine load and the temperature of the exhaust gas.
 17. The method of claim 9, heating the DEF injector above a normal operating temperature is accomplished by providing commands by the controller, said commands being arranged to increase at least one of a speed and a load output of the engine.
 18. A method for remediating a fault in a diesel exhaust fluid (DEF) injector, comprising: determining that a fault is present in the DEF injector, said fault being attributable to the condensation of crystalline urea within the injector after boiling and evaporation of water from an aqueous urea solution has occurred within the DEF injector; activating a failure signal when the fault in the DEF injector is present; heating the DEF injector to a temperature that is above a normal operating temperature to melt any crystalline urea within the DEF injector; continuing to heat the DEF injector while the temperature of the DEF injector is below a maximum threshold temperature and while a timer has not elapsed; periodically activating the DEF injector to evacuate any molten urea from within the DEF injector while the timer has not elapsed; and determining whether the fault has been remediated.
 19. The method of claim 18, wherein the DEF injector is adapted to operate in association with an exhaust system of an internal combustion engine disposed in a machine, and wherein heating the DEF injector above a normal operating temperature is accomplished by causing a temperature of exhaust gas of the engine to increase.
 20. The method of claim 19, wherein, when the failure has been remediated as evidenced by normal operation of the DEF injector while the timer has not lapsed, the method further includes causing the temperature of the exhaust to lower to a normal operating temperature. 